Compressor-unloading means



June 3 1924.

Filed Oct. 29. 1921 H C JOHANSEN COMPRESSOR UNLOADING MEANS ChicaPatented June 3, 1924.

UNITED STATES 1,496,543 PATENT orncs.

may O. JO, 0] GH'IOLGO, ILLINOIS, ASSIGNOB 'I'O SULLIVAN MACHINERYOOBJPOBA'IIOII', ADORPOMTION OF MASSACHUSETTS.

. oonnnssoniunmnnme mus.

Application October 39, 1931. Berti! I0. 511,380.

To all whom it may concern:

Be it known that I, Hannr O. Jonansmz, a citizen of the United States,residing at go, in the county of Cook and State of Illinois, haveinvented certain new and useful Improvements in Com ressor-UnloadingMeans, of which the fol owing is a full, clear, and exact specification.

My invention relates to compressor unloading means.

An object of my invention is to provide an improved com ressor unloadingmeans, and more especia y an improved compressor unloading means of theauxilia type adapted tobe used with a compressor avmg an intake typeunloader, and to avoid the compression of air which mi ht leak past" theintake unloader valve w en the compressor is turning over unloaded, froma partial vacuum to receiver pressure and -so the generation ofexcessive temperatures. Other objects and advantages ofmy invention willbe apparent in the course of the following specification and appendedclaims.

In the accompanying drawings, I have shown for pur ease of illustrationone embodiment whic my invention may assume in ractice.

these dra s,-

Fig. 1 is a side e evation of a com ressor provided with my improved onoading means.

2 is a detail view, partially in section, of the high ressure cylinder,showing the relationof e unloading means thereto.

Fig. 3 is a central longitudinal section through my improvedunloadipgwgec msm.

Fig. 4 is a transverse section on the line 44 of 'F' 3.

This mec anism is an improvement u on the mechanism illustrated in mycopen mg application for compressors, Serial No. 295,482, filed May 7,1919.

Referri to the drawings in which I have shown the illustrativeembodiment of my invention and particularl to Fig. 1, it W111 be notedthat I have own a compressor of the angle compound type havin ahorizontal low-p double acting cy inder 1, a high pressure double actingvertical cylinder 2, and drivi mechanisms for the pistons reciprocablean these cylinders whereby the two stages are operated from the singlecrank shaft 3. The intake to the low pressure cylinder 1 is through aninlet pipe 4 and is controlled by an automatically operated unloadingmeans 5, such as is in common use on compressors, to unload thecompressor by closing the intake thereto when the pressure in thereceiver or pressure discharge line exceeds a predetermined desiredamount. The partially compressed air or other fluid passes from the lowpressure cylinder through intercooler 6 to the hi h ressure cylinder 2and thence by way 0 a ischarge i e 7 to the point of use or to areceiver. en the pressure in the receiver, or other point to which thepipe 7 is connected, rises above the predetermined desired pressurenamed, the unloading means 5 is operated by automatic means which are sowell known as not to need description at this point and the intake tothe compressor is thereby closed and hence the compressor, if there isno leakage, no lon er operates to com ress air drawn in ihrolg the line4 and to discharge it to the In practice, it is possible that the intakecontrollin mechanism may not completely close all t e connection betweenthe pi 4 and the low pressure cylinder 1 or that t are 'may be otherleaka perhaps through the stufling boxes, an under those circumstancesthe continued reciprocations of the piston in the low pressure cylindermay draw in a reduced char of air into the low pressure cylinder w ichis insufl'icient to fil it at atmos heric pressure.- Therefore, at theend of the suction strokes the cylinder may have in it air at arelatively low pressure which air will be com ressed and forced lnto theintercooler. 's air which leaks by the intake unloading mechanism and ispassed into the intercooler is not materially compressed in the lowpressure cylinder by reason of the fact that the intercooler pressure ispum d down to a artial vacuum by the hi pressure cyllnder. Therefore, inthe high pressure cylinder, since the same condition prevails as in thelow pressure cylinder, i. e. that at the end of the suction stroke ofthe high pressure piston there is a artial vacuum in the hi h pressurecylin er, there occurs upon t e compression strokes of the piston acompzeession of a charge of air from perhaps t e pounds or more absoluteup to thepressureinthedisehargelineLsa 100 pounds gage or more. As aresult 0 the number of compressions during this operation, a veryconsiderable amount of heat is generated which at times may besuflicient to explode mixtures of gas and air formed in the h ressurecylinder from va mation of e ubricating oil, or, if this does not occur,to carbonize the lubricant in the pressure cylinder and so reduce thelabricat sficienc To avoid dificulty of this kin and aim ar trouble, Ihave mounted upon the high pressure cylinder 2 my improved unloadingmechanism which avoids the compression of fluid up to dis char linepressure and instead rnnts the sage of fluid from the big prescylin erto the atmosphere at ressures not greatly exceeding atmosp ericpressure.

My improved unloading mechanism is designated 8 and comprises a casmg mae u of three parts,-two and sections 9 an 10 and a central section 11.The end sections are bored to provide coaxial cylinders 12 and 13 and intheir normal tion these cylinders lie with their axes h iizontal. Thecentral section is rovided with a slightly enlarged bore an at its op'te ends has valve seating surfaces 14 an 15. Reciprocable in the clinders 12 and 13 are pistons 16 and 17 w ich are closed at theirad'acent ends and provided with rims 18 an 19 respectively adapted toseat u n the valve seating surfaces 14 and I5. hcse istons, asillustrated, have 0 rear end, t this is not requisite and t e rear endsthereof may be closed if desired. Between the adjacent closed ends ofthe pistons 15 and 16 is disposed a spring 20 which is of slightlygreater length than the distance between the valve seatin surfaces 14and 15. Each of the cylin era is provided with an enlarged annularcounterore at its end adjacent the central section 11, thesecounterbores being designated respectively 22 and 23. The rims 18 andltv are adapted to cooperate with the remote ends of these counterboresto limit the unseating movements of the valve pistons 15 and 16. Therear end of each cylinder is connected to the counterbore of the other,the rear end of cylinder 12 bein connected by s assage 24 to the counterre of the cylin er 13, while the rear end of the cylinder 13 isconnected to the counterbore 22 of the c linder 12 b a passage 25. Pipes26 and i connect t c Passages 24 and 25 to the op osite ends 0 thecylinder 2 at points so ocated that the connections will not be whollyoverrun by the piston. The bore of the central sectionof this unloadimeans is connected by "a port 28 control] by a spring pressed endseating valve 29 with an atmospheric vent 80.

The mode of operation of this mechanism will be readily apparent. Whenthe compressor is operating loaded, the pressure in the lines 26 and 27will vary between intercooler pressure 7 and compressor pressure. willremain constantly seated. When the intake to the low pressure cylinderis closed, the low pressure cylinder will no longer supply anyappreciable amount of air to the intercoolcr and the intercoole'rressure will be rapidly pum down by t e high pressure cylin er. ere willthen promptcome a time when the pressure on one of t e suction strokesof the piston will fall low enou to cause the air in the chamber betweene valves to open the valve whose rear end is connected to the end of thecylinder in which suction is taking place before the pressure on theother side 0 the dischar As a result the valves 15 and piston gets highenough to keep the valve closed. This .will result in the discharthrough port 28 of the premure in the h' ressure cylinder as soon as itreaches a 'ttle above awh eric pressure, and of course at such a temrature that no injurious result is possib e. The mechanism willtlfiareafier sct(as a relief means), connect! t swam i. e. compressingsides of t e piston to atmosphere whenever the pressure is until thecyhnder 1S reloaded. will evident that as one valve seats the spring,which is just a little longer than the distance between the two valveswhen seated, will cushion its seating and will aid in the unseating ofthe valve which is about to open. This arran ment produces a morecertain action of t e valves and practically eliminates all slapin ofthe valves upon their seats and r age resulting from that cause.

Whi e I have in this application specifically described one form which mmvention may assume in practice, it w' be understoo that this form ofthe same is shown for purposes of illustration and that the inventionmay be modified and embodied in various other forms without delpartingfrom its spirit or the scope of t e appended claims.

What I claim as new and dmire to secure by Letters Patent is:

1. An unloading mechanism for a compressor cylinder comprising a casing,a plurality of valves therein, 'a connection with the atmosphere,tpassages leading from each end of the cylin er to said casi and havingtheir communication with e atmospheric connections controlled by saidvalves, each of said valves being governed as to o the pressureconditions in that one of and connections which it does not control ands ring .meanscooperating with said valves an tending to unseat them whenth are seated.

2. An unloading mechanism for a compnessor cylinder comprising amultipart casing consisting of spaced cylinder sections connected by acentral section, cylinder bores in said cylinder sections, a centralbore in said central section in alinement with said cylinder bores andsurrounded by seat areas, counterbores in said cylinder sectionsadjacent said central sections, pistonsdis sed in said cylinders andhaving enlarge heads reciprocable in said counterbores and adapted tocooperate with said seat areas, a spring disposed in said central boreand of a length when uncompressed greater than the distance between saidpistons when the latter are seated, and connections each connecting oneend of said comressor cylinder with one of said counterres an theopposite end of the opposite cylinder.

3. An unloading mechanism for a compressor cylinder comprising a casing,a plurality of oppositely disposed valves therein, a connection with theatmos here between said valves, connections leading to the o?- positeends of the cylinder controlled y said valves, a. ring between saidvalves of a length slig tly eater than the distance between said va veswhen they are in their most proximate positions to each other, and meansfor causin said valves to alternately act as relief va ves.

In testimony whereof I aflix m si ature.

HABRY' C. J 0 EN.

